1. Field of the Invention
The present invention relates to a twin-clutch transmission including synchromesh.
2. Description of Background Art
As a twin-clutch transmission, the following one is known wherein transmission gears are pivotally supported by two coaxial main shafts and transmission gears are pivotally supported by a countershaft constantly mesh with each other corresponding to each transmission gear ratio. A sleeve is pivotally supported by at least one rotating shaft among the two main shafts and the countershaft in such a manner as to be restricted from relative rotation and be movable in the axial direction. The transmission gear is pivotally supported by the rotating shaft relatively rotatably and have sleeve teeth and gear dog teeth that mesh with each other. When the sleeve teeth mesh with the gear dog teeth due to the movement of the sleeve and a tarcome into shift stage is formed, two clutches are alternately connected and disconnected. This allows smooth gear shift to the tarcome into transmission gear ratio without interruption of power transmission of an internal combustion engine. See, for example, Japanese Patent Laid-Open No. 2008-215555.
Furthermore, among transmissions are ones including synchromesh. See, for example, Japanese Patent Laid-Open No. 2004-125112. In the synchromesh disclosed Japanese Patent Laid-Open No. 2004-125112, ring gear teeth (ring teeth) formed in an outer ring (synchronizer ring) of a blocking ring intervene between gear teeth (gear dog teeth) formed in a first transmission gear are pivotally supported relatively rotatably by a rotating shaft that is a main shaft or a countershaft and spline teeth (sleeve teeth) formed in a sleeve (synchronizer sleeve) pivotally supported by the rotating shaft in such a manner so as to be restricted from relative rotation and be movable in the axial direction. At the time of gear shift, due to the movement of the synchronizer sleeve, the sleeve teeth come into contact with and mesh with the ring teeth and then come into contact with and mesh with the gear dog teeth. Therefore, the synchronizer sleeve (and the rotating shaft) and the first transmission gear are joined to each other while synchronizing with each other.
A transmission is desired, that is obtained, by incorporating synchromesh like that disclosed in Japanese Patent Laid-Open No. 2004-125112 into a twin-clutch transmission in which two main shafts are coaxially formed with clutches each provided on the input side of a respective one of the main shafts being alternately connected and disconnected. See, for example, Japanese Patent Laid-Open No. 2008-215555.
In the twin-clutch transmission including such synchromesh, when the sleeve teeth comes into contact with the ring teeth of the blocking ring due to the movement of the synchronizer sleeve of the synchromesh, gear shift shock and a collision sound caused by the collision of them with each other need to be suppressed.
For this purpose, the movement speed of the synchronizer sleeve needs to be reduced immediately before the sleeve teeth come into contact with the ring teeth due to the movement of the synchronizer sleeve of the synchromesh. However, the movement position of the sleeve at which the sleeve teeth come into contact with the ring teeth involves a variation due to component tolerance. In addition, the sleeve teeth and the ring teeth also involve the progression of wear attributed to slide contact and change over the ages. Therefore, the movement position of the sleeve at which the sleeve teeth come into contact with the ring teeth also changes, i.e. the timing at which the sleeve teeth come into contact with the ring teeth also changes. Thus, the timing of the reduction of the movement speed of the synchronizer sleeve gradually deviates from the optimum timing and it becomes impossible to effectively reduce the gear shift shock and the collision sound.